Hydrazones

ABSTRACT

Compounds of the formula   WHEREIN R1 is hydrogen or methyl, n is 0 or 1 and R2 is   WHEREIN R&#39;&#39; is hydrogen or methyl and m is 0 or 1 and their utility as anti-ozonants in natural and synthetic rubbers.

United States Patent Ley et al.

[ 1 3,689,554 1 Sept. 5, 1972 [54] HYDRAZONES [72] Inventors: Kurt Ley, Odenthal-Globusch; Ernst Roos, Cologne, Flittard; Theo Kampermann, Cologne, Lindenthal; Roland Nast, Cologne, Buchheim,

[21] Appl. No.: 850,637

[52] US. Cl. ..260/557 H, 260/804, 260/459 R [51] Int. Cl ..C07c 109/18 [5 8] Field of Search ..260/557 H, 804

[56'] References Cited 7 UNITED STATES PATENTS 3,095,448 6/1963 Biel ..260/558 H Primary Examiner-Henry R. Jiles Assistant Examiner-S. D. Winters Attorney-Connolly and Hutz [57] ABSTRACT Compounds of the formula R1 R] H R] wherein R is hydrogen or methyl, n is 0 or 1 and R is wherein R is hydrogen or methyl and m is 0 or 1 and their utility as anti-ozonants in natural and synthetic rubbers.

5 Claims, No Drawings HYDRAZONES Vulcanizates of natural or synthetic rubber are known to develop cracks when their surface is under mechanical stress and exposed to atmospheric influences. The mechanical stress may be both constant in time, static, and periodically variable, dynamic. It is known that the ozone occurring in low concentrations I can be effectively protected against the development of cracks under the influence of ozone by the incorporation of derivatives of p-phenylene diamine such as N- isopropyl-N-phenyl-p-phenylene diamine and N-( 1,3- dimethylbutly)-N-phenyl-p-phenylene diamine.

The aforesaid p-phenylene diamine derivatives and similar anti-ozonants exert their effect by chemically reacting with ozone or with the primary ozonization products of rubber by a mechanism which is not known in detail but which deactivates the products promoting the development of cracks. It is also known that rubber can be protected against the effect of ozone by other methods, namely, by incorporating mixtures of macrocrystalline and microcrystalline waxes. By virtue of their partial insolubility, these waxes form a protective film over the surface of the vulcanizate which prevents the ozone molecules from penetrating and thereby prevents actual chemical reaction from taking place.

One disadvantage of the aforesaid p-phenylene diamines is their marked tendency towards discoloration. In cases where vulcanizates containing these products are exposed to light, they undergo a change in color varying from reddish-brown to brown-black. One disadvantage of using waxes is that the protective film can be broken, for example, when it is subjected to bending. In this case, deep ozone cracks are immediately formed.

It has now been found that compounds corresponding to the formula wherein R is hydrogen or methyl and m is or I are suitable for use as anti-ozonants for natural rubber or synthetic unsaturated rubber. These compounds do not In addition, the novel products do not discolor and accordingly do not suffer from the well-known disadvantage of the aforesaid derivatives of p-phenylene diamine.

The following products are typical examples of the additives used in accordance with the invention:

TABLE 1 l 1,2,5 ,6-tetrahydrobenzaldehyde)-hexahydrobenzoyl-hydrazone 2. (l,2,5,6-tetrahydro- 4-methyl-benzaldehyde)-hexahydro-benzoyl-hydrazone 3. (l,2,5,6-tetrahydrobenzaldehyde)-( 1 ',2',5",6- tetrahydrobenzoyl)-hydrazone 4. (1,2,5,6-tetrahydr0-2- dehyde)-(l ,2,5,6'5. benzaldehyde- 1 ,2 ,5 ,6-tetrahydrobenzoyD-hydraor 5-methylbenzal- T,2',5,6'-tetrahydrobenzoyl)-hydrazone 6. l ,2,5,6-tetrahydro-4-methyl-benzaldehyde)-( 1 ',2,5 ',6 '-tetrahydrobenzoyl)-hydrazone 7. 1,2,5,6-tetrahydrobenzaldehyde)-( 1 ',2',5 ,6- tetrahydro-4 methyl-benzoyl)-hydrazone 8. l ,2,5,6-tetrahydro-4-methyl-benzaldehyde)-( 1 ,2 ,5 ',6-tetrahydro-4 -methyl-benzoyl )-hydrazone 9. (1 ,2,5,6-tetrahydrobenzaldehyde l ',2,5 ',6- tetrahydro-l -methyl-benzoyl)-hydrazone 10. (1,2,5,6-tetrahydrobenzaldehyde)-( l ',2',5 ',6- tetrahydro-2 or S-methyl-benzoyl )-hydrazone l l. l ,2,5,6-tetrahydro-2,5-endomethylene-benzaldehyde)-( l ,2',5 ',6-tetrahydro-2,5 '-endomethylenebenzoyl )-hydrazone l2. l,2,5,-tetrahydro-acetophenone)-l ,2,5 ,6- tetrahydro-benzoyl)-hydrazone l3. 1,2,5,6-tetrahydro-3 or acetophenone)-(1 ',2',5 ,63 or 4'-methylbenzoyl )-hydrazone l4. l,2,5,6-tetrahydro-2,5-endomethyleneacetophenone)-( I ,2 ,5 ',6-tetrahydro-2,5 -endomethylene-benzoyl )-hydrazone The agents of the present invention can be satisfactorily processed with rubber and, when used in quantities sufficient to give the desired protective effect, do not show any efflorescence and hence, unlike the aforementioned waxes, no breakage of the protective film.

The processing of the rubber mixtures is not adversely influenced by the agents of the present invention. In particular, plasticity and pre-vulcanization behavior remain the same when the agents of this invention are added. However, the mechanical properties of the vulcanizate are affected to a limited extent. The degree of crosslinking decreases slightly, and this is reflected in a reduction in the stress value. However, this can readily be corrected without including other disadvantages by the addition of a vulcanization accelerator such as dibenzoyl disulphide and/or sulphur during the mixing process in quantities of up to 0.5 parts per hundred parts of rubber, based on the weight of the rubber.

The compounds according to the invention are generally added in quantities of from 0.3 to 5.0 parts per hundred parts of rubber, based on the weight of the rubber, preferably, in quantities of from 0.5 to 3.0 parts per hundred parts of rubber. Other antiagers may be included.

4-methyl- (1 ,2,5,6-tetrahydrol-methyl-- styrene,

The anti-ozonants used in accordance with the invention maybe employed in natural rubber and synthetic unsaturated elastomers containing double bonds, for example, in polymers of butadiene, isoprene, dimethyl butadiene and their homologs, also in copolymers of conjugated diolefins with polymerizable vinyl compounds such as, for example, styrene, methyl divinyl benzene, acrylonitrile, methacrylonitrile, acrylates or methacrylates and copolymers obtained from iso-olefins such as isobutylene or its homologs and small quantities of conjugated diolefins. It is also possible to protect polymers of the kind obtained from chlorobutadiene and copolymers of chlorobutadiene with monoand/or diolefins or polymerizable vinyl compounds.

The hydrazide hydrazones employed in accordance with the invention may be prepared, for example, by reacting the corresponding hydrazides with aldehydes or ketones. The procedure usually adopted is to react 1 mol of the hydrazide with 1 mol of the aldehyde or ketone in an organic solvent such as, for example, ethanol, methanol, isopropanol, acetonitrile, dimethyl formamide, benzene, cyclohexane or light gasoline at a temperature of from 10 C. to 100 C., the hydrazide hydrazones being formed in an exothermic reaction. They are worked up in the usual way. The water formed during the reaction may optionally be removed by azeotropic distillation.

The invention is illustrated by the following Examples in which the parts indicated are by weight.

EXAMPLE 1 Mixtures of the following compositions for the treads of automobile tires were prepared on mixing rolls:

A B C D E Test specimens prepared from these mixtures measuring 0.4' X 4.5 X 4.5 cm were vulcanized in a press for 30 minutes at 151 C. The test specimens were then fixed in a plastic frame in such a way that elongations of percent, percent and 30 percent respectively, were produced across their surfaces. The test specimens thus bent were weathered for three months in a southerly direction without any cover. Crack development was evaluated at certain intervals as specified in the following Table, by counting the total number of cracks visible with the naked eye and also by measuring their average length and then assigning ratings defined as follows:

Both ratings are reported in the following Table, the rating for the number of cracks being reported first, followed by the average length rating.

Elongation Days Wea thered Prior to Evaluation 0 2 8 20 50 Vulcanizate A (control) 10 0/0 2/1 4/1 4/2 4/2 4/3 20 4/1 5/1 5/2 5/3 5/3 30 0/0 5/1 6/1 6/2 6/2 6/2 Vulcanizate B 10 0/0 0/0 O/O 0/0 0/0 O/O 20 0/0 0/0 0/0 0/0 O/O 0/0 30 0/0 0/0 3/1 3/2 3/2 4/2' Vulcanizate C 10 0/0 O/O 0/0 0/0 0/0 0/0 20 0/0 0/0 0/0 0/0 0/0 0/0 30 O/O 0/0 0/0 O/O 0/0 2/4 Vulcanizate D 10 O/O 0/0 0/0 0/0 0/0 0/0 20 0/0 0/0 0/0 0/0 0/0 1/2 30 0/0 0/0 0/0 0/0 0/0 3/2 Vulcanizate E 10 0/0 0/0 0/0 0/0 0/0 0/0 20 0/0 0/0 0/0 0/0 0/0 0/0 30 0/0 0/0 0/0 O/O 0/0 2/3 The agents of the present invention did not cause any discoloration upon contact with the formulations specified in'Example 1. In addition, compounds 1, 2, 7 and 8 were incorporated in a pure white mixture based on light crepe, vulcanized in the usual way, and the vulcanizates were exposed to direct sunlight for a period of 2 months. There was no sign of any discoloration, i.e., the color of the vulcanizates were the same as the control having no added agents.

EXAMPLEZ I a. 77.4 g. (0.71 mol) of l,2,5,6-tetrahydrobenzaldehyde are added dropwise with stirring at 50 C. to a suspension of 80 g. (0.71 mol) of hexahydrobenzoic acid hydrazide. There is a rise in temperature to 56 C., the hydrazide enters into solution and, after a short while, a crystalline deposit is precipitated. The product is stirred for 1 hour, cooled, suction-filtered and washed with light gasoline. g. of 1,2,5,6- tetrahydrobenzaldehyde hexahydro-benzoyl hydrazone (Compound 1 from Table 1) is obtained in the form of colorless crystals. After dissolution in, and reprecipitation from methanol, this product melts at from 171 C. to 173 C.

b. In addition to benzene, light gasoline, methanol, isopropanol or acetonitrile may be used as solvents for the reaction described in Example 2a. The water formed during the reaction may optionally be removed by azeotropic distillation.

The removing agents of the present invention are prepared as in Example 2a. Typical examples are presented in the following Table.

Carbonyl component Hydrazide Compound (Table 1) Hydrazide hydrazine 1. A compound of the formula 3. The compound of claim 1 having the formula R1 'M C 0 H 'I 1I -N= CH,

4. The compound of claim 1 having the formula wherein R is hydrogen or methyl, n is 0 or 1 and R is R! l h R. V.

wherein R is hydrogen or methyl and mis 0 or 1.

2. The compound of claim 1 having the formula Tag? Q mine STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3, 9,55 Dated September 5, 1972 Kurt Ley, Ernst Roos, Theo Kempermann and Roland Nast Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

l- The format page, line 3 under item [72], "Kampermann" should read Kempermann Col. 1, line 20, "dimethylbutly)" should read dimethylbutyl) Col. 2, lines 16-19, should read 4. (l,2,5',6-tetrahydro- 2- or 5-methy1benza1dehyde)-'(1',2',5',6'-tetrahydrobenzoy1)- hydrazone line 20, should read 5.(l,2,5, 6-tetrahydro-lmethyl-benzaldehyde)-(l',2,5',6'-tetrahydrobenzoyl)-hydrazone lines 37-69, should read l3.(l,2,5,6-tetrahydro- 3- or t-methyL-acetophenone)-(l',2',5',6'-tetrahydro-3 or methyl-benzoyl)-hydrazone Col. 4, line 21, "5%" should read 0/0 Col. 6, the formula of claim 4 should read H H .l I

the formula of claim 5 should read 9 (H 0 C N N C Q CH Signed and sealed this 6th day of March 1973.

(SEAL) L Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. The compound of claim 1 having the formula
 3. The compound of claim 1 having the formula
 4. The compound of claim 1 having the formula
 5. The compound of claim 1 having the formula 